Tolerance to seed predation mediated by seed size increases at lower latitudes in a Mediterranean oak

Bogdziewicz M., Espelta J.M., Bonal R. (2019) Tolerance to seed predation mediated by seed size increases at lower latitudes in a Mediterranean oak. Annals of Botany. 123: 707-714.
Link
Doi: 10.1093/aob/mcy203

Abstract:

Background and Aims: The ability of plants to allocate energy to resistance against herbivores changes with abiotic conditions and thus may vary along geographical clines, with important consequences for plant communities. Seed size is a plant trait potentially influencing plant tolerance to endoparasites, and seed size often varies across latitude. Consequently, plant tolerance to endoparasites may change across geographical clines. Methods: The interaction between Quercus ilex (holm oak) and seed-predating Curculio spp. (weevils) was explored along most of the latitudinal range of Q. ilex. This included quantification of variation in seed size, survival likelihood of infested seeds, multi-infestation of acorns and community composition of Curculio weevils in acorns. Key Results: Larger seeds had a higher probability of surviving weevil attack (i.e. embryo not predated). Southern populations of oak produced on average four times larger seeds than those of northern populations. Consequently, the probability of survival of infested acorns decreased with latitude. The community composition of Curculio varied, with large weevils (C. elephas) dominating in southern populations and small weevils (C. glandium) dominating in northern populations. However, damage tolerance was robust against this turnover in predator functional traits. Furthermore, we did not detect any change in multi-infestation of acorns along the geographical gradient. Conclusions: Quercus ilex tolerance to seed predation by Curculio weevils increases toward the southern end of its distribution. Generally, studies on geographical variation in plant defence against enemies largely ignore seed attributes or they focus on seed physical barriers. Thus, this research suggests another dimension in which geographical trends in plant defences should be considered, i.e. geographical variation in tolerance to seed predators mediated by seed size. © 2018 The Author(s).

Read more

The effects of local climate on the correlation between weather and seed production differ in two species with contrasting masting habit

Bogdziewicz M., Szymkowiak J., Fernández-Martínez M., Peñuelas J., Espelta J.M. (2019) The effects of local climate on the correlation between weather and seed production differ in two species with contrasting masting habit. Agricultural and Forest Meteorology. 268: 109-115.
Link
Doi: 10.1016/j.agrformet.2019.01.016

Abstract:

Many plant species present inter-annual cycles of seed production (mast seeding), with synchronized high seed production across populations in some years. Weather is believed to be centrally involved in triggering masting. The links between meteorological conditions and seeding are well-recognized for some species, but in others consistent correlates have not been found. We used a spatially extensive data set of fruit production to test the hypothesis that the influence of weather on seed production is conditioned by local climate and that this influence varies between species with different life history traits. We used two model species. European beech (Fagus sylvatica) that is a flowering masting species, i.e. seed production is determined by variable flower production, and sessile oak (Quercus petraea) that is a fruit-maturation masting species, i.e. seed production is determined by variable ripening of more constant flower production. We predicted that climate should strongly modulate the relationship between meteorological cue and fruit production in Q. petraea, while the relationship should be uniform in F. sylvatica. The influence of meteorological cue on reproduction in fruiting masting species should be strongly conditioned by local climate because the strength of environmental constraint that modulates the success of flower-to-fruit transition is likely to vary with local climatic conditions. In accordance, the meteorological cuing was consistent in F. sylvatica. In contrast, in Q. petraea the relationship between spring temperature and seed production varied among sites and was stronger in populations at colder sites. The clear difference in meteorological conditioning of seed production between the two studied species suggests the responses of masting plants to weather can be potentially systematized according to their masting habit: i.e. fruiting or flowering. © 2019 Elsevier B.V.

Read more

Evidence of high individual variability in seed management by scatter-hoarding rodents: does ‘personality’ matter?

Feldman M., Ferrandiz-Rovira M., Espelta J.M., Muñoz A. (2019) Evidence of high individual variability in seed management by scatter-hoarding rodents: does ‘personality’ matter?. Animal Behaviour. 150: 167-174.
Link
Doi: 10.1016/j.anbehav.2019.02.009

Abstract:

The predation and dispersal of seeds by scatter-hoarding animals is one of the most studied processes in the context of animal–plant interactions. Seed management by these animals has been traditionally approached at the population level: the patterns documented in the field are assumed to be similar for all individuals of the population and the variability within the population is considered to be random noise. However, little is known about to what extent this variability responds to different and consistent behaviours between individuals. The aim of this study was to analyse the individual variation and consistency in behaviour of scatter-hoarding rodents within a population. As our model we used the wood mouse, Apodemus sylvaticus, a key disperser of holm oak acorns, Quercus ilex, which, in turn, suffers high predation pressure by the common genet, Genetta genetta. In two sets of laboratory experiments, we compared the variance and consistency in behaviours and acorn management due to individual differences with that due to manipulation, using genet scents, of the perceived predation risk. Genet scents reduced the activity (i.e. time out of the refuge) in all wood mice, but the differences and consistency in activity between individuals accounted for most of the variance. Also, mice showed different and consistent stress or relaxed behaviours. Most of the variance in seed management variables, such as dispersal distance and seed size selection, was explained by consistent differences between individuals across scent treatments. The increase in stress behaviours and decrease in relaxed behaviours were positively related to dispersal ability (i.e. longer distances and larger acorns). Our study highlights the importance of considering the individual component of behaviour in scatter-hoarding rodents. This fine-scale level, largely overlooked in the ecological framework, will help to increase our understanding of seed management by scatter-hoarding animals. © 2019 The Association for the Study of Animal Behaviour

Read more